A first-time visitor to any bio or chem lab will have many wonders to behold, but few as captivating as the magnetic stirrer. A motor turns a magnet which in turn spins a Teflon-coated stir bar inside the beaker that sits on top. It’s brilliantly simple and so incredibly useful that it leaves one wondering why they’re not included as standard equipment in every kitchen range.

But as ubiquitous as magnetic stirrers are in the lab, they generally come in largish packages. [BantamBasher135] needed a much smaller stir plate to fit inside a spectrophotometer. With zero budget, he retrofitted the instrument with an e-waste, Arduino-controlled magnetic stirrer.

The footprint available for the modification was exceedingly small — a 1 cm square cuvette with a flea-sized micro stir bar. His first stab at the micro-stirrer used a tiny 5-volt laptop fan with the blades cut off and a magnet glued to the hub, but that proved problematic. Later improvements included beefing up the voltage feeding the fan and coming up with a non-standard PWM scheme to turn the motor slow enough to prevent decoupling the stir bar from the magnets.

[BantamBasher135] admits that it’s an ugly solution, but one does what one can to get the science done. While this is a bit specialized, we’ve featured plenty of DIY lab instruments here before. You can make your own peristaltic pump or even a spectrophotometer — with or without the stirrer.

[via r/Arduino]

It takes a lot of power and energy to keep grass levels down to an appropriate level; especially when it’s hot out. If cool glasses of lemonade aren’t around, the task at hand may not be completed any time soon causing the unkempt blades of green (or yellow) vegetation outside to continue their path of growth towards the sun.

Instead of braving the oven-like temperatures which will inevitably drench the person in sweat, this solar powered robot has been created ready to take on the job. With the heart of an Arduino, this device shaves down the grass on a regular basis, rather than only chopping down the material when it gets too long. This helps to save electricity since the mower is only dealing with young and soft plants whose heads are easily lopped off without much effort.

Internally, the robot’s circuitry interfaces with an underground wiring system that defines the cutting zones within the lawn, and proves to be a simple, accurate, and reliable approach to directing the robot where to go. If the device travels under a shaded area, a battery kicks in supplying energy to the engine. When sunlight is available, that same battery accumulates the electricity, storing it for later.

There is also an interesting mechanism in place that allows the controller to detect if the wheels are moving properly or if one or more of them have locked up. This is done by using a reed sensor that has been added near the rear-pivoting wheel which is then operated by a small magnet that is inserted into that same wheel.

Obstacle recognition is accomplished in the front by an ultrasonic sensor that is connected to the I2C BUS. A brushless motor, used in the field of aeromodelling, was coupled into a cutting blade. With everything set up, the solar powered lawn mower is ready to be unleashed into the outside world of unsuspecting, growing plants.

Now sit back, relax, and let the robot do the work for you.

For more grass cutting related hacks, be sure to check out this remote-controlled lawn mower, and this monster truck lawn tractor that can go through water.

I've been trying to control a brushless motor (EMAX CF2812) via ESC with arduino, but so far I've had limited sucess. I've managed to start the motor, but I can't seem to get reproducible results.

The first success I've got was by following the instructions here. From there I also got the following code:

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Hello again everybody my name is chickenparmi, and I like robots.

Today I would like to show you my obstacle avoidance bot, with a difference. The difference with this bot is that it has been build onto an RC drift car, meaning it goes very fast and is very dangerous.

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So, i've been having some trouble lately and I can't seem to find a solution on the web. I've managed to controll a brushless motor through and ESC and arduino with PWM. Nothing too dificult. What I need now is a way to controll an inversion of the motor. Like you know, changing two of the wires from the motor makes it turn the other way around.

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